This section introduces aspects that may be helpful to facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art. Any techniques or schemes described herein as existing or possible are presented as background for the present invention, but no admission is made thereby that these techniques and schemes were heretofore commercialized, or known to others besides the inventors.
An antenna is typically directional or omni-directional. A directional antenna directs radio frequency (RF) signal power in a specific direction, while an omni-directional antenna distributes the power approximately equally in all directions. The structure of a directional antenna is typically very different from that of an omni-directional antenna. A directional antenna typically radiating elements mounted to a groundplane, focusing RF power in a single direction. An omni-directional antenna typically either has no groundplane, so the RF radiates about equally in all directions, or has multiple sets of radiating elements and groundplanes that each radiate equally to provide 360 degrees of coverage. Some antennas combine directional and omni-directional antennas in a single assembly, vertically stacking the antennas, e.g. with the omni-directional antenna on the bottom of the overall structure and the directional antenna stacked on top, or vice versa. Such structures may be physically too large for various reasons to be suitable.